What are the individual adjusters for specifically? For instance, I know blue is to lighten a color.

Blue, being the opposite of orange, will "neutralize" the orangeness of a too-orange foundation. It will not lighten it, unless your foundation is darker in tone than the blue mixer. If you need to lighten your foundation, white will do that. If your foundation is too red (or pink), the opposite of red is green, so you will want green drops. If your foundation is already too "neutral" or olive, red will be the best mixer for you. If your foundation is too yellow, you could try the purple drops. The darkest drops presumably just darken, or "dull" a too-light or too-bright foundation. You may find, like me, that you need a combination of several different drops to save your foundations. Unless you're using Temptu airbrush foundations, I would personally recommend using LA Girl's mixer pigments, since you get much (much) more in the bottle, and at a lower price.

Where is the green at tho???

You can get the green adjuster direct through Temptu's website or through CameraReadyCosmetics. Same price, just gotta pay shipping.

Can I airbrush with this paint?

Hi there. Thank you for your interest. The S/B Adjusters are a silicone-based formula that may be used to adjust undertones, deepen or lighten our S/B Foundations. Our entire S/B line was designed for airbrushing. If you have any further questions, please feel free to contact TEMPTU's Customer Care Team. Thank you!